Method for producing ti or ti alloy through reduction by ca

ABSTRACT

The invention is a method for producing Ti or Ti alloys through reduction of TiCl 4  by Ca, which can produce high-purity Ti metals or Ti alloys. A molten salt containing CaCl 2  and having Ca dissolved therein is held in a reactor cell, electrolysis is performed in the molten salt in the reactor cell, and particulate Ti or Ti alloys are generated in the molten salt by supplying a metallic chloride containing TiCl 4  to the molten salt so as to react with Ca generated on a cathode electrode side by the electrolysis, allowing enhancement of a feed rate of TiCl 4  as a raw material of Ti, and also a continuous operation. Further, the method by the invention eliminates the need of the separate handling of Ca, because a reducing reaction and an electrolytic reaction can simultaneously proceed in the reactor cell to replenish Ca, consumed in the reducing reaction, by the electrolytic reaction. Accordingly, the production method by the invention can be used as means for efficiently and economically producing high-purity Ti metals or Ti alloys.

TECHNICAL FIELD

The present invention relates to a method for producing Ti or Ti alloysthrough reduction by Ca, in which a metallic chloride containingtitanium tetrachloride (TiCl₄) is reduced by Ca to produce Ti metals orTi alloys.

BACKGROUND ART

A Kroll method for reducing TiCl₄ by Mg is generally used as a methodfor industrially producing the Ti metals. TiCl₄ is obtained bychlorinating titanium oxide (TiO₂). In the Kroll method, the Ti metalsare produced through a reduction step and a vacuum distillation step. Inthe reduction step, TiCl₄ is reduced by Mg in a reactor vessel. In thevacuum distillation step, unreacted Mg and MgCl₂ formed as a by-productare removed from the sponge metallic Ti produced in the reactor vessel.

In the reduction step, the reactor vessel is filled with the molten Mg,and the TiCl₄ liquid is supplied from above on a liquid surface of themolten Mg. This allows TiCl₄ to be reduced by Mg near the liquid surfaceof the molten Mg to generate the particulate metallic Ti. The generatedTi metals move sequentially downward. At the same time, the molten MgCl₂which is of the by-product is generated near the liquid surface. Aspecific gravity of molten MgCl₂ is larger than that of the molten Mg.The molten MgCl₂ which is of the by-product moves downward due to thespecific-gravity difference, and the molten Mg emerges in the liquidsurface instead. The molten Mg is continuously supplied to the liquidsurface by the specific-gravity difference substitution, and thereducing reaction of TiCl₄ proceeds continuously.

In the production of Ti metals by the Kroll method, a high-purityproduct is produced. However, the production cost is increased and theprice of the product becomes remarkably expensive. One of factors ofincreased production cost is the difficulty in enhancing a feed rate ofTiCl₄. The following items (a) to (c) are cited as the reason why thefeed rate of TiCl₄ is restricted.

(a) In order to improve productivity in the Kroll method, it iseffective to enhance the feed rate of TiCl₄, i.e., to enhance a supplyamount of molten Mg to the liquid surface per unit area or unit time.However, when the feed rate of TiCl₄ is excessively enhanced, the rateof the specific-gravity difference substitution cannot keep up with thereaction rate, so that while MgCl₂ remains in the liquid surface, TiCl₄is supplied to the MgCl₂. As a result, the supplied TiCl₄ becomes lowergrade chloride gases (referred to as “unreacted gas”) such as anunreacted TiCl₄ gas and a TiCl₃ gas, and the unreacted gas is dischargedoutside the reactor vessel, which reduces utilization efficiency ofTiCl₄. It is necessary to avoid the generation of the unreacted gas,because a rapid increase in inner pressure of the reactor vessel isassociated with the generation of the unreacted gas. Thus, there is alimit of the feed rate of TiCl₄ because of the above reasons.

(b) When the feed rate of TiCl₄ is enhanced, Mg vapor generated from theliquid surface of the molten Mg reacts with TiCl₄ vapor to increase aprecipitation amount of Ti in the inner surface of the reactor vesselabove the liquid surface of the molten Mg. On the other hand, the levelof the liquid surface of the molten Mg rises as the reducing reactionproceeds. Therefore, the precipitated Ti in the inner surface of theupper portion of the reactor vessel is immersed in the molten Mg at alater stage of the reducing reaction, which causes the effective area ofthe Mg liquid surface to be decreased to reduce the reaction rate. Inorder to suppress the decrease of reaction rate, it is necessary thatthe feed rate of TiCl₄ be restricted to prevent the Ti precipitation inthe inner surface of the upper portion of the reactor vessel.

Japanese Patent Application Publication No. 8-295955 proposes a methodin which the reaction efficiency is enhanced by supplying liquid TiCl₄in a dispersive manner to the liquid surface in which the molten Mgexists, and thereby the Ti precipitation is suppressed in the innersurface of the upper portion of the reactor vessel. However, the methodproposed in Japanese Patent Application Publication No. 8-295955 is notenough to suppress the Ti precipitation.

(c) In the Kroll method, because the reaction is performed only near theliquid surface of the molten Mg in the reactor vessel, an exothermicarea is narrowed and the temperature is locally elevated. Therefore,cooling becomes difficult, so that the feed rate of TiCl₄ is restricted.

Although the feed rate of TiCl₄ is not directly affected, in the Krollmethod, Ti is generated in the particulate form near the liquid surfaceof the molten Mg, and aggregated because of wetting properties (adhesionproperties) of the molten Mg, and the Ti particles is made move downwardwhile aggregated, and then the Ti particles are sintered to grow the Tiparticles by the heat generated from the molten liquid during thedownward travel. Therefore, it makes difficult to recover the generatedTi by taking out Ti as fine particles to the outside of the reactorvessel, whereby the continuous production is difficult to perform andthe improvement of the productivity is fettered. By reason of this, theTi is produced in the batch process in the form of the sponge titanium.

With reference to the Ti production methods except for the Kroll method,for example, U.S. Pat. No. 2,205,854 describes that, in addition to Mg,for example, Ca can be used as the reducing agent of TiCl₄. U.S. Pat.No. 4,820,339 describes a method for producing Ti through the reducingreaction by Ca, in which the molten salt of CaCl₂ is held in the reactorvessel, the metallic Ca powder is supplied into the molten salt fromabove, Ca is dissolved in the molten salt, and TiCl₄ gas is suppliedfrom below to react the dissolved Ca with TiCl₄ in the molten salt ofCaCl₂.

In the reduction by Ca, the Ti metals are generated from TiCl₄ by thereaction of the following chemical formula (1), and CaCl₂ as theby-product is also generated at the same time:TiCl₄+2Ca→Ti+2CaCl₂  (1)

Ca has an affinity for Cl stronger than that of Mg, and Ca is suitableto the reducing agent of TiCl₄ in principle. Particularly, in the methoddescribed in U.S. Pat. No. 4,820,339, Ca is used while dissolved in themolten CaCl₂. When the reducing reaction by Ca is utilized in the moltenCaCl₂, an area (reaction field) where the reaction is created isenlarged compared with the Kroll method in which TiCl₄ is supplied tothe liquid surface of the reducing agent in the reactor vessel.Therefore, because the exothermic area is also enlarged to facilitatethe cooling, the feed rate of TiCl₄ can be largely enhanced, and theremarkable improvement of the productivity can be also expected.

However, the method described in U.S. Pat. No. 4,820,339 is hardlyadopted as the industrial Ti production method. In the method, becausethe highly expensive metallic Ca powder is used as the reducing agent,the production cost is higher than that of the Kroll method.

U.S. Pat. No. 2,845,386 describes another Ti production method (Olsenmethod) in which TiO₂ is directly reduced by Ca not through TiCl₄. Themethod described in U.S. Pat. No. 2,845,386 is a kind of oxidedirect-reduction method and is highly efficient. However, the oxidedirect-reduction method is not suitable to the production of thehigh-purity Ti because it is necessary to use high-purity TiO₂.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a method foreconomically producing a high-purity Ti metals or high-purity Ti alloyswith high efficiency, without using an expensive reducing agent.

In order to achieve the above object, the present inventors consider itindispensable that TiCl₄ be reduced by Ca, and the present inventorslook into the method for utilizing Ca dissolved in the molten salt ofCaCl₂ described in U.S. Pat. No. 4,820,339.

In the method described in U.S. Pat. No. 4,820,339, Ca in the moltensalt is consumed in the reducing reaction reactor vessel as the reactionexpressed by the chemical formula (1) proceeds, and it is necessary tocontinuously supply the metallic Ca powder to the reduction reactorvessel. However, in order to industrially establish the method forproducing Ti through reduction by Ca, the present inventors propose amethod for controlling a dissolved Ca concentration in the molten saltby electrolysis, in consideration of the fact that it is necessary thatthe consumed Ca of the molten salt in the reducing reaction iseconomically replenished.

That is, when the molten CaCl₂ is electrolyzed in a reactor cell,electrode reactions expressed by the following chemical formulas (2) and(3) proceed to generate a Cl₂ gas near the surface of a anode electrodewhile generating Ca near the surface of a cathode electrode, whichallows the Ca concentration to be increased in the molten salt.Therefore, when TiCl₄ is supplied to CaCl₂ so as to react with Cagenerated on the cathode electrode side, because Ca consumed in the Tigeneration is replenished as needed, the replenishment of metallic Cafrom the outside or extraction of metallic Ca becomes unnecessary, whichallows the Ti metals to be economically produced.Anode electrode: 2Cl⁻→2e⁻+Cl₂  (2)Cathode electrode: Ca²⁺+2e⁻→Ca  (3)

The method for replenishing Ca, consumed in the reduction of TiCl₄, withCa generated by the electrolysis can also be achieved by respectivelyperforming the reduction and the electrolysis in a reduction cell and anelectrolytic cell to circulate the molten CaCl₂ between the cells.However, when TiCl₄ is supplied to the molten CaCl₂ in the reactor cellso as to react with Ca generated on the cathode electrode side by theelectrolysis, the reactor cell can commonly be used as the reductioncell and the electrolytic cell. Therefore, because it is not necessaryto separately provide the reduction cell and the electrolytic cell,there is also a great advantage from a viewpoint of installation costcompared with the case in which the molten CaCl₂ is circulated betweenthe reduction cell and the electrolytic cell.

The present invention is made based on the above conception, and thegist of the present invention pertains to a method for producing Ti orTi alloys.

That is, a method for producing Ti or Ti alloys through reducingreaction by Ca includes: a reduction electrolysis step comprisingholding a molten salt in a reactor cell to perform electrolysis in themolten salt in the reactor cell, the molten salt containing CaCl₂ andhaving Ca dissolved in the molten salt and generating Ti or Ti alloys inthe molten salt by supplying a metallic chloride containing TiCl₄ to themolten salt so as to react with Ca generated on a cathode electrode sideby the electrolysis; and a Ti separation step of separating Ti or the Tialloy from the molten salt in the reactor cell or outside the reactorcell.

The method of the present invention for producing Ti or Ti alloysthrough reduction by Ca is a method of reducing TiCl₄ in which ahigh-purity material is easily obtained, so that the method of thepresent invention can produce high-purity Ti metals or high-purity Tialloys.

Ca is used as the reducing agent to cause the metallic chloridecontaining TiCl₄ to react with Ca in the molten salt containing CaCl₂,so that the feed rate of TiCl₄ can be increased. Because the Tiparticles or Ti alloy particles are generated in CaCl₂, the aggregationof the particles and the particle growth caused by the sintering aresignificantly lessened, whereby it becomes possible to discharge theseparticles outside reactor cell, thus enabling the continuous operationto be performed. The reducing reaction and the electrolytic reaction aresimultaneously caused to proceed, and Ca is replenished by theelectrolytic reaction while consumed in the reducing reaction, whichallows Ca to be utilized in the state in which Ca is always dissolved inthe molten salt.

Accordingly, the production method of the present invention canefficiently and economically produce high-purity Ti metals orhigh-purity Ti alloys.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a Ti metal production apparatus whichexhibits an embodiment mode according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION 1. Contents of Ti or Ti AlloyProduction Method According to the Invention

In the method according to the present invention for producing Ti or Tialloys through reduction by Ca, for example, when the molten CaCl₂ isheld as the molten salt in a reactor cell to supply TiCl₄ to the moltensalt in the reactor cell, TiCl₄ is reduced by Ca dissolved in the moltensalt to generate Ti metals in the form of the particulate or powder(hereinafter referred to as “Ti particles”). Although the Ca dissolvedin the molten salt is consumed in association with the generation of theTi particles, Ca is generated on the cathode electrode side to replenishthe consumed Ca dissolved in the molten salt because the electrolysis ofthe molten CaCl₂ proceeds simultaneously with the reducing reaction inthe reactor cell.

One of the reasons why the Ca is not conventionally used in theindustrial production of the Ti metals is the difficulty in separatingCa and CaCl₂. Mg is produced by electrolyzing MgCl₂, and the generatedMg can efficiently be recovered because Mg is hardly dissolved in MgCl₂.Similarly to Mg, Na can efficiently be produced by electrolyzing NaCl.On the other hand, Ca is produced by electrolyzing CaCl₂, and it isdifficult to efficiently separate only Ca because the generated Ca isdissolved in CaCl₂ by about 1.5%. There is also a phenomenon in whichthe dissolved Ca generates CaCl₂ by a back reaction (reaction in whichCa generated on the cathode electrode side is combined with Cl₂generated on the anode electrode side to return to CaCl₂). Therefore,the production efficiency of Ca becomes worse. In this regard, althougha recovery factor of Ca is improved by applying the contrivance such ascooling the electrode, the production cost of Ca inevitably remains tobe still high.

In contrast, in the method of the present invention for producing Ti orTi alloys through reduction by Ca, Ca dissolved in the molten CaCl₂ isused and the separation of Ca is not necessary, so that the electrolysisproduction cost of Ca can be decreased.

When the reduction by Ca is utilized in the molten CaCl₂, the reducingreaction field is expanded and the heat generation/exothermic area isalso enlarged. Mg has vapor pressure of 6.7 kPa (50 mmHg) at 850° C.while Ca has extremely small vapor pressure of 0.3 kPa (2 mmHg).Therefore, in the case where Ca is used for the reduction, the Tiprecipitation amount becomes dramatically lessened in the inner surfaceof the upper portion of the reactor cell compared with Mg. Accordingly,in the method of the present invention for producing Ti or Ti alloysthrough reduction by Ca, the feed rate of TiCl₄ can largely beincreased.

In addition, Ca is inferior in wetting properties (adhesion properties)to Mg, and Ca adhering to the precipitated Ti particles is dissolved inCaCl₂, so that the aggregation in the generated titanium particles andthe particle growth caused by the sintering are significantly lessened.Therefore, the generated Ti can be taken out from the reactor cell inthe form of particles, and the Ti production can continuously beoperated.

For a supply mode of TiCl₄ to the molten CaCl₂ liquid, it isparticularly desirable that TiCl₄ be directly supplied in the gaseousstate inside the molten CaCl₂ liquid, because the contact efficiency ofTiCl₄ to Ca in the molten CaCl₂ liquid is enhanced. Alternatively, it isalso possible that TiCl₄ is supplied in the gaseous or liquid state tothe liquid surface of the molten CaCl₂ liquid, or it is also possiblethat the liquid or gaseous TiCl₄ is supplied to the liquid surface orinside the molten Ca liquid held on the molten CaCl₂ liquid.

In the case where the reducing reaction is performed by supplying theTiCl₄ liquid to the liquid surface of the molten Ca held on the surfaceof the molten CaCl₂ liquid, it is desirable that the molten Ca liquid beheld in a thin state to an extent in which Ca in the molten CaCl₂ liquidcan be utilized. When the Ca layer is thin, because Ca in the moltenCaCl₂ liquid is also involved in the reaction, the reaction is renderedto take place at the molten Ca layer as well as at the molten CaCl₂layer, and the Ti can continuously be generated even if thespecific-gravity difference substitution cannot keep up with thereaction rate due to the increase in feed rate of TiCl₄.

With reference to the supply of the TiCl₄ gas, an advantage of themethod of the present invention for producing Ti or Ti alloys throughreduction by Ca over the Kroll method will be described as below.

In the Kroll method, the TiCl₄ liquid is supplied to the liquid surfaceof the molten Mg liquid. It is tried that the TiCl₄ gas is supplied intothe molten Mg liquid in order to enlarge the reaction field. However, asdescribed above, because the Mg has the high vapor pressure, the Mgvapor intrudes in a supply nozzle of the TiCl₄ gas to react with TiCl₄,which causes a supply nozzle to be choked.

On the other hand, it is also tried that the TiCl₄ gas is suppliedinside the molten MgCl₂ liquid. Although a choking frequency of thesupply nozzle is decreased, the supply nozzle choking problem stillremains. This is attributed to the fact that the melt is agitated bybubbling of the TiCl₄ gas and sometimes the molten Mg reaches the supplynozzle. As much as anything, even if TiCl₄ is supplied inside the moltenMgCl₂ liquid, the reducing reaction is difficult to occur because Mg ishardly dissolved in the molten salt.

On the contrary, in the method of utilizing the reduction by Ca, thenozzle choking is hardly generated and the TiCl₄ gas can be suppliedinside the molten CaCl₂ liquid. One of the reasons why the nozzlechoking is hardly generated is the small vapor pressure of the moltenCa.

That is, in the method of the present invention for producing Ti or Tialloys through reduction by Ca, it is particularly desirable that TiCl₄be directly supplied in the gaseous state inside the molten CaCl₂liquid, and this supply mode can be applied without any problem in theactual operation. It is also possible that the liquid or gaseous TiCl₄is supplied to the liquid surface of the molten CaCl₂ liquid, or it isalso possible that the liquid or gaseous TiCl₄ is supplied to the liquidsurface or inside the molten Ca liquid held on the molten CaCl₂ liquid.

In separating the Ti particles generated in the molten CaCl₂ liquid, itis possible to separate the Ti particles from the molten CaCl₂ liquideither in the reactor cell or outside the reactor cell. However, theseparation becomes the batch process when the separation is performed inthe reactor cell. In order to improve the productivity, the Ti particlesand the molten CaCl₂ liquid may be separated from each other outside thereactor cell by utilizing the Ti generated in the particulate form todischarge the Ti particles outside the reactor cell along with themolten CaCl₂ liquid. The Ti particles can simply be separated from themolten CaCl₂ liquid by a squeezing operation and the like by means ofmechanical compression.

In the case where Ti is produced by the method of the present invention,usually TiCl₄ is used as a raw material. The Ti alloy can also beproduced by using a mixture of TiCl₄ and other metallic chloride.Because TiCl₄ and other metallic chloride are simultaneously reduced byCa, the Ti alloy can be produced by this method. Said other metallicchloride may be used either in the gaseous or liquid state.

In the method of the present invention for producing Ti or Ti alloysthrough reduction by Ca, the back reaction and the wearing of thereactor material become of issues. In the back reaction, Ca (Cagenerated on the cathode electrode side or unreacted Ca) in the moltenCaCl₂ is combined with Cl₂ generated on the anode electrode side toreturn to CaCl₂. The wearing of the reactor material is caused by highreactivity of Ca.

When the back reaction is generated, the electrolytic current isconsumed for the back reaction, which decreases current efficiency.Particularly, for the back reaction in which Ca generated on the cathodeelectrode side is combined with Cl₂ generated on the anode electrodeside, it is desirable to separate the inside of the cell into the anodeelectrode side and the cathode electrode side by providing a partitionwall (see FIG. 1) whose lower portion is opened.

For the problem of the wearing of the reactor material, the molten saltis formed not by single CaCl₂ but by the mixed salt, and a melting pointof the molten salt is decreased to effectively decrease the temperatureof the molten salt (namely, bath temperature).

That is, in the method of the present invention for producing Ti or Tialloys through reduction by Ca, basically CaCl₂ having the melting pointof 780° C. is used as the molten salt. However, a binary system moltensalt such as CaCl₂—NaCl and CaCl₂—KCl and a ternary system molten saltsuch as CaCl₂—NaCl—KCl can also be used such that at least one kind ofother salts (for example, NaCl, KCl, LiCl, and CaF₂) is mixed to CaCl₂to form a multiple system molten salt. Therefore, because the meltingpoint of the salt is decreased, the temperature of the molten salt (bathtemperature) can be decreased. For example, when CaCl₂ and NaCl (havingthe melting point of about 800° C.) are mixed together, the meltingpoint can be decreased to about 500° C. at the lowest.

As a result, the extension of reactor material life and the reactormaterial cost reduction can be achieved, and further the vaporization ofCa or the salt can be suppressed from the liquid surface.

2. Embodiment Mode of Ti or Ti Alloy Production Method of the Invention

An embodiment mode of the present invention will be described below withreference to the drawing.

FIG. 1 is a block diagram showing a Ti metals production apparatusaccording to an embodiment mode of the present invention. A reactor cell1 in which the reducing reaction and the electrolytic reaction areconcurrently generated is used in the embodiment. The reactor cell 1holds the Ca-rich molten CaCl₂ in which a relatively large amount of Cais dissolved. CaCl₂ has the melting point of about 780° C., and themolten salt of CaCl₂ is heated to the temperature of the melting pointor more.

In the reactor cell 1, the molten CaCl₂ which is of the molten salt iselectrolyzed by passing the electric current between a anode electrode 2and a cathode electrode 3, the Cl₂ gas is generated on the side of anodeelectrode 2, and Ca is generated on the side of cathode electrode 3. Inthe example, the inside of the reactor cell 1 is divided into the anodeelectrode side and the cathode electrode side by a partition wall 4.However, in the partition wall 4, the lower portion is opened in orderthat the transfer of the molten salt is not prevented.

In the reactor cell 1, the gaseous TiCl₄ is injected in the dispersivemanner inside the molten salt on the cathode electrode side in parallelwith the electrolysis of the molten salt. Therefore, the injected TiCl₄is reduced to generate the particulate metallic Ti by the Ca dissolvedin the molten salt. The generated Ti particles moves downward by thespecific gravity difference and accumulated at the bottom on the cathodeelectrode side in the reactor cell 1.

The Ti particles accumulated at the bottom of the reactor cell 1 aredischarged from the reactor cell 1 along with the molten salt existingat the bottom of the reactor cell 1, and the Ti particles and the moltensalt are sent to the Ti separation step (not shown). In the Tiseparation step, the Ti particles discharged along with the molten saltfrom the reactor cell 1 are separated from the molten salt.Specifically, the Ti particles are compressed to squeeze the moltensalt. The Ti particles obtained in the Ti separation step is melted toyield Ti ingots.

On the other hand, the molten salt separated from the Ti particles inthe Ti separation step is the molten salt after use, in which Ca isconsumed to decrease the Ca concentration. It is desirable to reuse themolten salt after use by returning it to the reactor cell. Usually, boththe above separated molten salt and the molten salt after use separatelydischarged from the reactor cell 1 are introduced to the anode electrodeside in the reactor cell 1.

Ca in the molten salt is consumed on the cathode electrode side in thereactor cell 1 as the Ti particles are generated by the reducingreaction. However, Ca is generated near the surface of the cathodeelectrode 3 in the cell by the electrolysis which proceedssimultaneously in the cell, and a consumed amount of Ca is replenishedby the Ca generated by the electrolysis. That is, TiCl₄ supplied intothe molten salt is sequentially reduced in a direct manner by Cagenerated near the surface of the cathode electrode 3.

On the other hand, in the desirable mode, the molten salt after use issent from the Ti separation step onto the anode electrode side in thereactor cell 1. Therefore, a unidirectional flow of the molten salt isformed from the anode electrode side toward the cathode electrode sidein the reactor cell 1 to avoid the flow of Ca generated on the cathodeelectrode side into the anode electrode side. When the partition wall 4shown in FIG. 1 is provided, the flow of Ca into the anode electrodeside is effectively prevented by the combination of the partition wall 4and the formation of the unidirectional flow. Thus, the molten saltintroduced onto the anode electrode side in the reactor cell 1 is movedonto the cathode electrode side to be replenished with Ca and to becomeas the Ca-rich molten salt, thereby enabling to be reused for thereducing reaction.

It is desirable that the Cl₂ gas generated on the anode electrode sidein the reactor cell 1 be reused in a chlorination step (not shown). Inthe chlorination step, TiCl₄ which is of the raw material of Ti isgenerated by the chlorination of TiO₂. The generated TiCl₄ is introducedto the reactor cell 1, and TiCl₄ is circularly used to generate the Tiparticles by the Ca reduction.

As described above, in this embodiment mode, the generation of the Tiparticles by the Ca reduction, i.e., the Ca consumption and the Careplenishment by the electrolysis are concurrently performed in thereactor cell 1. Therefore, it is not necessary to replenish or take outCa in the solid state, and the high-quality Ti particles arecontinuously and economically produced by the Ca reduction. The reactorcell 1 is commonly used as the reduction cell and the electrolytic cell,which contributes largely to an economical merit from the viewpoint ofinstallation. The flow of Ca generated on the cathode electrode sideinto the anode electrode side is avoided in the reactor cell 1, so thatthe back reaction in which Ca reacts with the Cl₂ gas generated on theanode electrode side can be prevented.

During the operation, the molten salt is managed at a temperature higherthan the melting point (about 780° C.) of CaCl₂ in the reactor cell 1.

INDUSTRIAL APPLICABILITY

According to the method of the present invention for producing Ti or Tialloys through reduction by Ca, the feed rate of TiCl₄ which is of theraw material can be enhanced, and the continuous production can berealized. Further, the reducing reaction and the electrolytic reactionare simultaneously caused to proceed in the reactor cell, and Caconsumed in the reducing reaction can be replenished by the electrolyticreaction, so that it is not necessary to independently handle Ca byitself.

Accordingly, the production method of the present invention caneffectively be used as means for efficiently and economically producinghigh-purity Ti metals or high-purity Ti alloys, so that the productionmethod of the present invention can widely be applied as the industrialmethod for producing Ti or Ti alloys.

1. A method for producing Ti or Ti alloys through reduction by Ca,comprising: a reduction electrolysis step which is consisted of holdinga molten salt in a reactor cell to perform electrolysis in the moltensalt in the reactor cell, the molten salt containing CaCl₂ and having Cabeing dissolved in the molten salt, and of generating Ti or the Tialloys in the molten salt by supplying a metallic chloride containingTiCl₄ to the molten salt so as to react with Ca generated on a cathodeelectrode side by the electrolysis; and a Ti separation step ofseparating Ti or the Ti alloys from the molten salt in the reactor cellor outside the reactor cell.